Romney put gentle but unmistakable distance between his agenda and Ryan's hot-potato budget proposals on Sunday as the new team soaked up excitement from partisans in North Carolina and Ryan's home state of Wisconsin. But Democrats weren't about to let them off that hook.

President Barack Obama's senior campaign adviser David Axelrod deemed Ryan's budget "the Ryan-Romney plan" and cast the new addition to the Republican ticket as a "right wing ideologue."

"It is a pick that is meant to thrill the most strident voices in the Republican Party, but it's one that should trouble everybody else -- the middle class, seniors, students," Axelrod said Sunday on CNN.

Romney walked a careful line as he campaigned with Ryan by his side in North Carolina. Romney singled out Ryan's work "to make sure we can save Medicare." But the presidential candidate never said whether he embraced that plan himself. During the Republican primary, Romney had called Ryan's budget a "bold and exciting effort" that was "very much needed."

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Ryan proposed to reshape the long-standing entitlement by setting up a voucher-like system to let future retirees shop for private health coverage or choose the traditional program -- a plan that independent budget analysts say would probably mean smaller increases in benefits than current law would provide.

Romney aides, echoing talking points they circulated to party leaders and operatives, praised Ryan's budget work, but sought to draw a distinction between his ideas and Romney's. They were clearly mindful that some of Ryan's proposals don't sit well with key constituencies, among them seniors in critical states like Florida and Ohio.

"Gov. Romney is at the top of the ticket," Romney spokesman Kevin Madden told reporters Sunday. "And Gov. Romney's vision for the country is something that Congressman Ryan supports,"

On CNN, Romney senior adviser Ed Gillespie said Romney would have signed Ryan's proposed austere budget if it landed on his desk as president. But he also emphasized that Romney would "be putting forward his own budget" if he wins the election.

Romney's selection of Ryan has jolted the presidential contest, until now one that had done little to draw the public's attention, and set the contours for the fall campaign: Romney as a proponent of a friendlier business climate seeking to revitalize the economy and rein in federal spending and Obama casting himself as a defender of middle-class families and federal spending on health care, retirement pensions and education.

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The running mate pick also shifted the campaign debate, at least temporarily, to the pressing economic challenges facing the country -- a debate both Romney and Obama have said they wanted to have even as the dialogue had spiraled into nasty, personal attacks. Sunday was a marked departure from the previous week, when the race for the White House devolved into name-calling and accusations of lying from both campaigns.

Three months from Election Day, polls find Obama with a narrow lead over Romney, though the race remains tight in key battleground states. And while Ryan's selection raised the role of government spending and Medicare in the election, the fundamentals of the campaign remained unchanged: a race defined by a weak economy and high unemployment, measured most recently at 8.3 percent in July.

Romney, seeking to pull his campaign out of a summer slump, appeared to relish in campaigning alongside the youthful and energetic Ryan.

"This is Day Two for me," a gleeful Romney told a campaign rally in Moorseville, N.C. "This is Day Two on our comeback tour to get America strong again, to rebuild the promise of America." He meant a comeback for the country, but that could apply as well to his campaign.

The duo blitzed through North Carolina -- a competitive battleground state in the November election -- as part of a multistate bus tour. The pair was ending the day in Waukesha, Wis., with a homecoming-themed event for Ryan. Romney then planned to head to Florida and Ohio as the week begins, while Ryan was scheduled to travel to Iowa on Monday as the ticket looked to cover as much ground as possible.

For Ryan, the weekend of campaigning was a chance to make a first impression on many voters. A recent CNN/ORC international poll found a majority of voters had no opinion of the congressman, an up and comer in Washington but far from a household name. Nearly 40 percent had never heard of him and 16 percent weren't sure what they thought of him.

The 42-year-old congressman embraced the attack dog role traditionally assumed by the No. 2 on the ticket. He said Obama had turned his 2008 campaign slogan of "hope and change" into "attack and blame."

"We're not going to fall for it," Ryan told a crowd of 5,000 in High Point, N.C.

Obama, pushed to the background as Romney and Ryan dominated the weekend, was in his hometown of Chicago on Sunday hosting a series of birthday-themed campaign fundraisers.

The president and Vice President Joe Biden were fanning out Monday for a series of campaign events. The president was starting a three-day bus tour of Iowa, signifying the importance of the toss-up Midwestern state, while Biden headed to North Carolina and Virginia.

Obama's campaign had already been trying to tie Romney to Ryan's tough budget blueprint even before the Wisconsin congressman emerged as a contender for the GOP ticket. Democrats believe seniors, those nearing retirement and middle-income voters will view Ryan's long-term budget plan remaking Medicare and cutting trillions in federal spending as a threat to their financial security.

Campaign officials were readying state-specific strategies aimed at seniors in Florida and Ohio, and also planned to court young people and military service members who they believe will be turned off by other elements of Ryan's proposed budget cuts.

As chairman of the House Budget Committee, Ryan is the primary author of conservative tax and spending proposals that the tea party-infused Republican majority approved over vigorous Democratic opposition in 2011 and again in 2012.

They envision transforming Medicare into a program in which future seniors would receive government checks that they could use to purchase health insurance. Under the current program, the government directly pays doctors, hospitals and other health care providers.

Ryan and other supporters say the change is needed to prevent the program from financial calamity. Critics argue it would impose ever-increasing costs on seniors.

Other elements of the budget plan would cut projected spending for Medicaid, which provides health care for the poor, as well as food stamps, student loans and other social programs that Obama and Democrats have pledged to defend.

In all, it projects spending cuts of $5.3 trillion over a decade and would cut future projected deficits substantially. Romney, too, has proposed ambitious cuts in federal spending, but without the specifics that make Ryan's plan so attractive to fiscal conservatives and such a target for Democrats.

Republicans say Ryan could help put Wisconsin, which traditionally has voted Democratic in presidential campaigns, in play and that the Catholic Midwesterner also could appeal to blue-collar voters whom Romney, a Mormon and multimillionaire, has struggled to reach in Iowa and elsewhere.

Obama's campaign argues Ryan's budget could be a powerful campaign tool for them in states like Pennsylvania and Iowa, in addition to Florida and Ohio.

Down ballot, party leaders hoped to work in tandem with Obama to turn the Ryan budget into a litmus test in congressional races, forcing Republican opponents to take ownership of the plan. The campaign arm of the House Democrats, for example, was urging its lawmakers to call Ryan's budget plan -- not the man himself -- Romney's new "running mate."